I recently purchased a Lost Round nose fish - a Twin Fin setup is recommended. It has 5 Fin boxes for FCS II.
I already have a set of Quads - Large FCS II Performer. And I'm not that keen on spending another $200 ish for A set of Fcs twin fins if they are the same shape/ specs as the quad fins.
1. Can I just use the 2 front fins from the quad fins. Or are they different alltogether
2. With 5 fin boxes - where would they be placed ideally?

My previous boards had fins glassed in - so New territory.
Cheers in advance for ay useful info!
If using the set of quads put the whole set in, even though it is designed as a twin fin , the quad set will work and possibly even bring out some finer points of the boards capability.
if it rides well, enjoy, if it doesn't and you want to ride it as a twin with the quad set it is suggested to use the front two fins /fin boxes however the fins will not be amazing, they will work and it will ride ok/good and possibly excellent but highly likely no where as well as it does as a quad.
if you want to ride it as a pure twin have a look at some different designs a semi keel is a great option these fins will have 130-150%+ of the surface area of the two front fins of your quad set this will also ensure that the boards capacity to accelerate and the twin fin experience is not compromised.
put up a pic of the fin set up,??
if it's a Matt biolis lost put the quad set straight in and get out there
Razz - Mate That info is spot on - as far as addressing my questions
The board is a Round Nose Fish Redux Carbon Wrap (Epoxy Carbon Wrap) - 6' 0" x 21" x 2 3/4" x 39.5L - FCS II
Images below
I will do as suggested and place the full quad set in and if it's noticeably off then try taking the back 2 out. If I buy anything perhaps just 2 smaller rear Quads than the ones shown in the next post

I had one of these for a while in Firewire timbertek construction.
Rode like a pig with Keel fins in, but went really well with MR 2+1 fins and as a quad.
I ended up cracking the glass on the deck in front of the tail pad and the whole thing filled with water.
The reef removed the rear quads for me today. Lost
current verdict is the QUAD. goes super quick down the line, holds/ works the with the rail to hold Top to bottom no dramas.
The twin - slower? Too loose for me anyway.
FCS 2 - first bad experience. Need to put a Screw in a think.
